In known power generators disclosed in Japanese Unexamined Patent Application Publication No. 54-116610 and No. 6-86517, as shown in FIG. 8, the entirety of a rotor is constructed by penetrating a drive shaft 1 through a bracket 2 serving as an outer casing with bearings 3 interposed therebetween, arranging a field winding 5 around an outer periphery of a yoke 4 which is externally fitted over and fixed to the drive shaft 1, and arranging claw poles 6 and 7 which are alternately projected from the left and right sides of the field winding 5. On the other hand, a stator winding 8 is attached to the bracket 2 in an opposed relation to the claw poles 6 and 7. Further, electric power supply to the field winding 5, i.e., power feeding, is performed through a slip ring 9 in a sliding way.
In the above-described construction, it is here thought that, by supplying a DC current to the field winding 5 through the slip ring 9, an N pole is generated on the right side of the field winding 5, as viewed on the drawing, and an S pole is generated on the left side of the field winding 5, as viewed on the drawing. In such a case, the N pole is induced in the claw pole 6 projecting from the right side, and the S pole is induced in the claw pole 7 projecting from the left side. Stated another way, by providing only one field winding 5 which is wound about the drive shaft 1, a plurality of N poles and S poles can be alternately generated in the circumferential direction around an outer periphery of the rotor.
There is also known a motor provided with inductors, similarly to the above-described construction of the power generator.
However, because the field winding 5 is formed as a part of the rotor and power feeding to the field winding 5, which is rotated, has to be performed through the slip ring 9, i.e., the sliding contact, the structure is complicated. Further, the useful life is shortened due to contact wear of the slip ring 9. Still another problem is that if the sliding contact at the slip ring 9 is unstable, the power feeing also becomes unstable.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 54-116610
Patent Document 2: Japanese Unexamined Patent Application Publication No. 6-86517